The disclosure of Japanese Patent Application No. 2000-131185 filed on Apr. 28, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a vehicular deceleration control apparatus and method for adding deceleration to a vehicle and, more particularly, to a vehicular deceleration control apparatus that detects the state of operation of an accelerator and adds deceleration to a vehicle in accordance with the state of operation, and to a method of controlling a braking system.
2. Description of Related Art
As an art related to the invention, a deceleration control apparatus that adds deceleration to a vehicle by generating a braking force when an operating person discontinues depression of an accelerator pedal is disclosed in Japanese Patent Application Laid-Open No. 9-95222. The deceleration control apparatus described in this laid-open patent application adds a braking force to a main brake system when the accelerator pedal is within a deceleration range.
If this deceleration control apparatus is installed in a vehicle, it becomes unnecessary to operate the brake pedal frequently when the vehicle is to be gently accelerated or decelerated. Furthermore, deceleration responsiveness is enhanced. Thus, easy driving can be realized.
However, the aforementioned laid-open patent application does not disclose detection of or response to a failure in the system.
Accordingly, the invention provides a vehicle deceleration control apparatus capable of detecting a system abnormality during an early period.
In order to achieve the foregoing, a vehicular deceleration control apparatus in accordance with a first aspect of the invention includes an accelerator operation state detector and a deceleration adder. The apparatus controls the additional deceleration based on a target deceleration set in accordance with detection results by the accelerator operation state detector. The deceleration control apparatus of the invention determines whether the system is abnormal based on a deviation between the target deceleration and a detected actual deceleration.
A vehicular deceleration control apparatus in accordance with a second aspect of the invention includes an accelerator operation state detector and a deceleration adder. The apparatus controls the additional deceleration by the deceleration adder in accordance with detection results by the accelerator operation state detector. The deceleration control apparatus of the invention determines whether the system is abnormal based on a deviation between a target braking torque to be applied by the deceleration adder and a detected actual braking torque.
A vehicular deceleration control apparatus in accordance with a third aspect of the invention has an accelerator operation state detector and a deceleration adder. The apparatus controls the additional deceleration by the deceleration adder in accordance with detection results by the accelerator operation state detector. The deceleration control apparatus of the invention determines whether the system is abnormal based on a correspondence between the state of operation of the accelerator and the actual deceleration.
If the deceleration adder has an abnormality, the actually applied deceleration will not equal a target deceleration. According to the invention, it is possible to determine whether the system is abnormal by detecting a braking torque or a deceleration that is actually generated, and by examining a deviation between the detected braking torque or deceleration and a braking torque or deceleration that is to be generated or examining a correspondence between the detected braking torque or deceleration and the state of operation of the accelerator. Thus, the invention makes it possible to detect an abnormality in the deceleration control system during an early period, and to prompt an operator to take an appropriate measure.
If it is determined that the system is abnormal, the deceleration added by the deceleration adder may be decreased with a predetermined time gradient. Therefore, it becomes possible to discontinue the deceleration adding control without sharply changing the deceleration, if it is determined that there is an abnormality.
The deceleration adder may add a deceleration by operating a braking device that applies braking torque to a wheel based on a braking operating performed by the operator. In this case, the deceleration adder constitutes a braking system as well. Therefore, an abnormality in the braking system can be detected during an early period.
The invention is not limited to the aforementioned vehicular deceleration control apparatus. Further aspects of the invention include, for example, a vehicle equipped with a vehicular deceleration control apparatus, and a method of controlling a braking system that applies deceleration to a vehicle.